1. Field of the Invention
The present invention relates to a wafer handling apparatus of a semiconductor treatment system. More particularly, the present invention relates to a wafer handling apparatus capable of conveying a wafer into a process chamber and/or withdrawing the wafer from the process chamber while the wafer treatment processing is being carried out.
2. Description of the Related Art
In general, a semiconductor treatment system has a process chamber and a handler which conveys a wafer into the process chamber and/or withdraws the wafer from the process chamber. An example of such a handler is disclosed in U.S. Pat. No. 5,746,565 (issued to Tepolt on May 5, 1998). The wafer conveyed into the process chamber is manufactured into a semiconductor device or semiconductor chip through a number of processes including lithography, chemical and physical deposition, and plasma etching processes.
Polymers are commonly generated in the process chamber while the above processes are being carried out. In particular, a significant amount of polymers are intentionally generated in the dry etch process so as to treat the wafer. Furthermore, polymers are inevitably generated in a CVD (chemical vapor deposition) process which forms, at a high temperature, a thin film of polycrystalline material, such as Si, Si.sub.3 N.sub.4, and SiO.sub.2, on the wafer disposed in the process chamber.
After the processes have been completed, most of the polymers are discharged out of the process chamber by a vacuum pump. However, some of the remaining polymers float and stick to the side wall of the process chamber having a relatively lower temperature. As a result, with the lapse of time, the amount of polymer on the side wall of the process chamber increases and form aggregates of polymer particles. Such polymer particles can drop onto the wafer being treated, thereby decreasing the quality of the semiconductor device. In addition, the side wall of the process chamber must be manually cleaned periodically in order to remove the polymer particles, resulting in a consumption of time and labor.
In order to overcome the above problem, a method of preventing polymer from sticking to the side wall of the process chamber by heating the side wall or periphery of the process chamber has been suggested. This method is based on the concept that polymers do not stick to high temperature objects. According to the above method, the side wall, lid or electrode installed in the process chamber is heated by a specially manufactured heater to prevent the polymers from sticking to the side wall of the process chamber.
One example of the heating method for the process chamber is disclosed in U.S. Pat. No. 5,516,283. According to the above patented heating method, the outer surface of the process chamber is directly heated by a heater. In addition, heating pads or heating tubes can be installed on the lid of the process chamber or on the side wall of the process chamber.
FIGS. 1 and 2 show a conventional semiconductor treatment system 100 having a process chamber heating apparatus.
As shown in FIGS. 1 and 2, a conventional semiconductor treatment system 100 has a loadlock chamber 70 having a handler 10 therein, and a process chamber 80 having an electrode 85 therein.
The handler 10 is operated by a handler driving apparatus 12, which is controlled by a controller 60, to thereby convey a wafer 110 stored in a cassette chamber (not shown) onto the electrode 85 of the process chamber 80. A support 15 for supporting the handler is disposed beneath the handler 10.
A gate 72 is installed at a partition between the loadlock chamber 70 and the process chamber 80. The gate 72 is operated by a gate operating apparatus 73, which is controlled by the controller 60, to thereby close/open an inlet 75 formed in the partition.
A lid 55 forming the top of the process chamber 80 is provided with a duct (not shown) for supplying a gas into the process chamber 80. Both the lid 55 and the side wall 82 of the process chamber 80 are connected to a heater 50. The lid 55 and the side wall 82 of the process chamber 80 are heated by the heater 50 so that polymers 90 floating in the process chamber 80 do not stick to the side wall 82 of the process chamber 80. The heater 50 is also controlled by the controller 60.
The conventional semiconductor treatment system 100 having the above-described structure operates as follows.
When the semiconductor manufacturing process begins, the controller 60 issues an operating signal to the handler driving apparatus 12 so that the handler 10 moves into the cassette chamber in which wafers 110 are stored.
Then, the handler 10 grips one wafer 110 using a vacuum and conveys the wafer into the process chamber 80. At this time, the controller 60 issues an electric signal to the gate operating apparatus 73 so that the gate 72 moves down, thereby opening the inlet 75 formed in the partition between the loadlock chamber 70 and the process chamber 80.
The handler 10 moves into the process chamber 80 passing through the inlet 75 and returns to its initial position after placing the wafer 110 onto the electrode 85 disposed in the process chamber 80. At the same time, the controller 60 issues an electric signal to the gate operating apparatus 73 so that the gate 72 moves up, thereby closing the inlet 75.
After the process has finished, the controller 60 again issues an electric signal which directs the gate operating apparatus 73 to open the inlet 75. At the same time, the controller 60 issues an electric signal to the handler driving apparatus 12 which causes the handler to move into the process chamber 80.
Then, the handler 10 grips the wafer 110 using a vacuum and moves into the cassette chamber whereupon the handler 10 places the wafer 110 into a slot of the cassette chamber.
While the above process is being carried out, the controller 60 operates the heater 50 so as that the lid 55 or the side wall 82 of the process chamber 80 is heated, whereby the polymers 90 floating in the process chamber 80 are prevented from sticking to the side wall 82 of the process chamber 80.
However, although the conventional semiconductor system 100 can prevent the polymers 90 from sticking to the side wall 82 of the process chamber 80, it cannot prevent the polymers 90 from sticking to the handler 10.
Typically, the initial temperature of the process chamber, in which a CVD, etching or ion implantation process is carried out, is about 50-120.degree. C. On the other hand, the initial temperature of the handler moving into the precess chamber is about 20-25.degree. C. Thus, polymers floating in the process chamber may stick to the handler 10 when the handler moves into the process chamber.
The polymers which stick to the underside of the handler gradually aggregate as polymer particles, which are then especially likely to fall onto the wafer being treated while the handler moves in the process chamber. Such polymer particles are in fact frequent causes of defects in the semiconductor devices.
For this reason, the handler must be disassembled from the system and cleaned periodically, which action consumes time and labor, and thereby detracts from the efficiency of the semiconductor manufacturing process.